1. Field of the Invention
This invention relates generally to the field of completing oil and gas wells and, more particularly, to a single trip system for perforating and gravel (or frac) packing a wellbore section. The system includes a unique hydraulic setting tool which is less sensitive to the hydraulic shocks generated from the detonation of the system""s tubing conveyed perforating guns than setting tools for previous single trip systems. A preferred embodiment of the system also utilizes a pump down shifting tool which mechanically unlocks the hydraulic setting tool so that the gravel pack packer may be set in the desired location. The service assembly of the system may include a concentric check valve in the service assembly for use when reversing out excess slurry following the completion of the gravel (or frac) pack operations.
2. Description of the Related Art
Single trip perforating and gravel pack systems have been available in the oil industry since at least the 1980""s. The detonation of the perforating guns create high shock loads which may adversely effect the rest of the system. Following detonation of the guns, rapidly expanding gas and displaced fluid around the perforating guns combine to create a hydraulic shock wave that travels at approximately 24,000 feet per second. The hydraulic shock wave travels through both the perforating and gravel packing system as well as the annulus around the system. These shock waves can cause numerous problems including prematurely setting the gravel pack packer at the wrong location in the wellbore and prematurely activating the annulus release mechanism which releases the service assembly from the gravel pack packer. Either of these and other possibly undesirable events may cause expensive fishing trips and/or multiple trips into the wellbore to remove and replace the perforating and gravel pack system.
Single trip perforating and gravel packing systems include a tubing conveyed perforating assembly, a gravel pack completion assembly, which includes a gravel pack packer, and a service assembly which includes a hydraulic setting tool for setting the gravel pack packer and a crossover tool assembly for conducting the gravel pack operations. Prior art hydraulic setting tools typically included an annulus release mechanism which utilized annulus pressure on the backside of the gravel pack packer to release the service assembly from the packer after the gravel pack packer had been set. The annulus release mechanism of the prior art setting tool included a piston which was separate and apart from the setting piston for the gravel pack packer. Thus, there was a risk that the hydraulic shock wave from the detonation of the perforating gun would actuate the hydraulic annulus release tool and prematurely release the service assembly from the gravel pack packer before the latter had been set.
The prior art setting tools also included a second hydraulic piston which hydraulically actuated a rotational lock between the service assembly and the gravel pack packer. This piston also actuated a preset lock feature that kept locking keys engaged with the setting sleeve of the packer. When this piston was shifted by hydraulic pressure, it unlocked the preset locking device on the hydraulic setting tool in order to commence setting the gravel pack packer. The piston also unlocked the rotational lock between the service assembly and packer assembly. This second piston was also susceptible to the hydraulic shock loads generated from the detonation of the perforating guns which could cause the premature release of the preset and rotational locks.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set for above. More particularly, the present invention has eliminated the separate hydraulic actuating pistons for the annulus release mechanism, the rotational lock and the preset lock device. The preferred embodiment of the hydraulic setting tool for the present invention includes an annulus release, a preset lock and a rotational lock. These features, however, are now mechanically actuated instead of hydraulically actuated. In addition, the present system mechanically locks the various assemblies in position so that the system will be more resistant to the shock waves generated by the detonation of the perforating guns. This is accomplished by shear pinning the mechanical components at higher values than traditionally used to better withstand the hydraulic shock wave traveling up both the annulus as well as the system itself.
An improved single trip perforating and gravel pack system is provided which includes a new hydraulic setting mechanism which is less sensitive to hydraulic pressures generated by the detonation of the perforating guns. Most hydraulic pistons have been eliminated from the hydraulic setting tool for the gravel pack packer which would normally be sensitive to hydraulic shocks generated from the perforating gun detonation. The annulus release mechanism of the service assembly operates off the packer setting piston rather than a separate annulus pressure sensitive piston. By working off the large setting piston, it is possible to shear pin components of the system at high shear values to withstand the severe shock loads created by perforating. The system also includes a mechanical lock sleeve which is preferably pressure balanced, includes no o-ring seals, and mechanically keeps the gravel pack packer from prematurely setting. The system utilizes a pump down shifting tool to engage and shift the lock sleeve to the unlocked position so the setting tool may begin setting the gravel pack packer. The pump down shifting tool is adapted to be permanently locked in place below the gravel flow ports after the lock sleeve has been shifted to the unlocked position. A double cup design may be used to insure that the shifting tool is pumped past the elongated gravel flow ports without partially blocking the ports at any time.
The preferred embodiment of the system is also designed to allow circulation from the workstring all the way through the gravel pack screens and out a circulating sub above the perforating guns prior to setting the service packer. The system includes a full opening internal diameter to the firing head so a detonating bar may be dropped to fire the perforating guns. A secondary firing system may also be used which is actuated by tubing pressure to hydraulically fire the perforating guns. In order the transfer tubing pressure to a hydraulic firing head, a sliding sleeve in the completion assembly is run in the closed position. The sleeve is later opened prior to commencing gravel packing operation to create a flow path from inside the service assembly, through the completion assembly, to the annulus below the gravel pack packer. The sliding sleeve is opened by engaging the sleeve with a shifting tool in the service assembly and shifting the sliding sleeve to the open position.
A preferred embodiment of the present invention incorporates a concentric check valve in the service assembly which improves well control and allows for reversing out excess slurry in the service assembly following completion of a gravel packing operation. Due in part to the configuration of the concentric check valve, the service assembly has an open internal diameter throughout which permits circulation of fluids through the service assembly, as well as the ability to drop a detonating bar or apply hydraulic pressure to the firing head for the perforating guns.